A simple but approximate method of pedigree evaluation is presented with particular reference to dairy cattle. It involves the expression of information available on any animal in the pedigree in terms of the equivalent number of ‘standard progeny records’. Formulae are given for the transfer of evidence from generation to generation within the pedigree. The application to one rather complex pedigree is illustrated and it is shown that the loss of information through the approximation is small.

The effects of birth weight, maternal age and parity on survival of single lambs have been studied in a Blackface and a Welsh Mountain flock.

In both flocks the maximum survival rate was found to occur among lambs with birth weights just above the mean. Mortality increased as lambs' birth weight increased or decreased from the optimum, but was especially heavy at the lower extreme of the range of birth weights.

Mortality decreased with age of dam to 14·3% for lambs from 4- to 6-year-old Blackface ewes and to 9·4% for lambs of 3- to 4-year-old Welsh ewes. Ewes having their first lambs gave mortality rates twice as great as for the mature ewes in the same flocks. The lower chances of survival of first born lambs irrespective of dam's age accounts for the apparent trend of mortality with maternal age in the Blackface.

Changes in mortality rates associated with variation in lamb's birth weight and with the age structure of the ewe flock were estimated. Possible means of improvement of survival rate are discussed.

Twenty-four Hereford × Angus × Shorthorn steers, which were 18 months old, were divided at random into four groups of six. There were four treatments, two involving the feeding of supplementary protein and two involving implantation of the steers with hexoestrol, thus:

(1) basic ration, no hexoestrol;

(2) supplementary protein, no hexoestrol;

(3) basic ration, hexoestrol implant;

(4) supplementary protein, hexoestrol implant.

While the hexoestrol implantation produced a significantly higher growth rate, the addition of protein, above the level in the basic ration, had no effect.

Blood samples from 262 Polish Red Cattle, 9 Danish Red Cattle and 123 cattle produced by crossing were examined for the presence of 45 erythrocyte antigenic factors.

The frequencies of most of the factors are given and estimates are made of the appropriate gene frequencies within the Polish Red breed as a whole.

Segregation of 42 B alleles was observed of which 9 have not previously been reported. The H′ factor hitherto recorded as marking an independent system is assigned to the SU system on genetical grounds and renamed S2.

It is concluded from the blood group data that the Polish Red breed has signs of a genetic relationship with Holstein-Friesian, Brown Swiss and Guernsey breeds but the relationship with the Danish Red breed is closer. The existence of the new alleles distinguish the Polish Red breed of cattle from all others investigated.